1. Technical Field
The present invention relates to a print data processing method, a print data processing device, and a print data processing system for appropriately printing on both sides of a receipt or other recording medium in a POS system, for example.
2. Related Art
POS systems used in retail stores that issue receipts printed on both sides by a receipt printer connected to the POS terminal are known from the literature. The store name, transaction details, and a barcode containing an ID code for identifying a particular transaction, for example, may be printed on the front of the receipt while a coupon or advertising, for example, may be printed on the back.
Japanese Unexamined Patent Appl. Pub. JP-A-2009-123028 teaches a POS system that has a receipt printer for duplex printing. The receipt printer in this POS system has a first head that prints on one side of the receipt paper, and a second head that prints on the other side, and attempts to eliminate receipt paper waste by dividing and printing the transaction information in areas on both sides of the receipt paper outside the areas where fixed information such as advertisements and a store logo is printed to predetermined locations on the receipt paper so that the length of the receipt is as short as possible.
In addition to the printer taught in JP-A-2009-123028, other duplex printers print on both sides of the paper using a single printhead by reversing and refeeding cut-sheet media passed the printhead as taught in Japanese Unexamined Patent Appl. Pub. JP-A-H06-171158, or print on both sides by means of two printheads disposed to opposing positions with the recording medium conveyance path therebetween as taught in Japanese Unexamined Patent Appl. Pub. JP-A-H10-129018.
When receipts are thus printed on both sides, however, the content printed on the reverse side may be visible from the front, or the printing on the back may bleed through to the front. If printing on one side thus overlaps printing on the other side, the readability of information printed on the front may be undesirably reduced.
For example, when printing with an inkjet head, the ink deposited on one side may bleed through to the other side. When a thermal head is used for printing both sides of the paper, the heat-sensitive coating on the surface of one side may change color when the other side is printed, a problem also referred to herein as “bleed-through.” When a graphic that is dark or has a high print density is printed on the back, the content printed on the back may be visible through the paper when reading the printing on the front. These problems of bleed-through and transparency occur particularly easily when using thin paper.
If printing on the reverse side bleeds through or is visible on the other side where content, such as a linear or two-dimensional barcode, that is intended to be read optically is printed, the scanning accuracy of the barcode or other content is easily reduced.